A standard approach to increase redundancy in a node to node communication for connections in a communication network, such as an Asynchronous Serial Interface (ASI) connection or an Ethernet connection, is to use duplicated transmission paths, channels or links, between the communicating nodes, which herein after is referred to as a 1+1 connection. Typically, a receiving node is arranged to receive replicas of a data stream, a stream of packets, from a transmitting node. The replicated data streams are transported via a main link and via a backup link to the receiving node. Note that a link may refer to a sequence of intermediate node to node communications. Based on the quality or status of the communication over the respective link, a select mechanism in the receiving node determines which one of the links should be selected as a main link from which an output data stream of the node is forwarded to another node or an application associated with the node. Thus, the general idea of such 1+1 connection is that if the main link suffers malfunction, a failover can be performed to the backup link. However, due to for instance different time delays for the communication over the main link and the backup link, if the main link suddenly malfunctions, hits in the form of data loss or duplicated data in the forwarded data stream are normally incurred at the failover.
Instead of switching the communication link as a whole at a malfunction, it has been shown that the selection of which replicated data to forward can be performed on basis of identifiers included in the respective packets of a data stream. European Patent Application Publ. No. EP 0854 610 A2 discloses a redundancy method for an Ethernet communication between a plurality of nodes which are connected to each other through a first and a second independent Ethernet communication line. Identical data packets, each to which a data identifier for identifying data contents has been added, are transferred from a transmitting node to a receiving node over both communication lines. At reception, data transferred over the first and the second link is temporarily stored in a respective buffer, and in the receiving node it is determined on basis of the data identifier, which data transferred over the two respective communication lines that has arrived first, and which is therefore accepted as first reception data for further use. This provides a redundancy method with minimized introduced delay for the respective data portions while maintaining redundancy in the connection.